The present invention relates to a reflector of a vehicular low beam headlight.
Conventional vehicular low beam headlights have a fundamental configuration in which a coil-like filament is disposed in the vicinity of the focus of a paraboloid-of-revolution reflector with the central axis of the filament extending along the optical axis of the reflector (what is called C8-type arrangement), and a shade is placed under the filament to produce a cutline (or cut-off line) in a light-distribution pattern.
In this case, the part of the light emitted from the filament and going toward the lower half of the reflector is shielded by the shade and does not contribute to the formation of a light-distribution pattern. A resultant light-distribution pattern, which is formed on a screen located in front of the reflector at a predetermined distance, becomes a generally semi-circular pattern having a first cutline forming a certain angle with the horizontal center line and a second cutline extending along the horizontal center line.
A horizontally spread low beam light-distribution pattern is finally obtained as a result of light-distribution control by diffusive lens steps of an outer lens that is disposed in front of the reflector.
In recent years, with the streamlined styling of vehicle bodies which is required from the aerodynamic characteristics and designing, headlights need to be designed so as to conform to what is called the slant-nose shape of the front portion of vehicle bodies. More specifically, headlights should be vertically thin and have a large slant angle (i.e., an angle between the outer lens and the vertical direction).
It is not appropriate to provide highly diffusive lens steps on the outer lens having a large inclination in the manner as in the conventional case. (The provision of highly diffusive lens steps would cause a phenomenon that tailing of light occurs at the right and left end portions of the light-distribution pattern.) This will impose a serious limitation on the design of lens steps.
On the other hand, the use of the shade, which unavoidably causes an unusable reflector area, i.e., reduces the ratio of light flux utilization, is not preferable for the thinning of the headlight. It is desired to effectively use the entire area of the reflector to provide the horizontal spread and a clear cutline in the light-distribution pattern.